1. Field of the Invention
The present invention relates in general to an endoscope apparatus for obtaining image data based on the reradiated light generated from an observation portion upon the irradiation thereof with an excitation light, and in particular to an endoscope apparatus for obtaining image data of an observation area having at least two types of marks thereon.
2. Description of the Related Art
In the field of medicine, there are known endoscope apparatuses which utilize an imaging element such as a CCD or the like for converting an optical image to an electric signal which are used to obtain image data of an observation area. By displaying the images obtained by a CCD on a monitor or the like, these endoscope apparatuses feature the advantage of enabling simultaneous observation of the image by a plurality of people. In addition, by subjecting an obtained image to various image processes before displaying said image, characteristics of the image can be enhanced so that an image also including changes in tissue structures not visible to the naked eye can be displayed on a monitor, making a great contribution to the advancement of medicine.
In recent years, much progress has been made in development efforts relating to the memory apparatuses with which theses types of endoscope apparatuses are equipped. As a result, it has become a common practice to store obtained image data in an internal or external memory, and when an image of the same portion is again obtained and displayed, the previously obtained image data of the same portion is read out and displayed so that a comparative diagnostic reading both of the images can be performed. This type of comparative diagnosis is oftentimes performed in regard to ascertaining the change occurring over time in a diseased portion, in particular, when medication or other treatment is being administered.
When displaying images on a monitor or the like to perform this type of comparative diagnosis, it is desirable that the display state of the vicinity of the diseased portion, e.g. the magnification, display angle and the like, of the previously obtained image data (hereafter referred to as reference image data) should match that of the presently obtained image data (hereafter referred to as comparison image data), so as to improve the accuracy of the diagnosis.
However, when an image is to be obtained using an endoscope apparatus, in view of the complexity of the form of the vicinity of the observation area, and the variance in the direction of expansion of a body cavity, there are cases in which the form of the observation area itself is different, whereby it is difficult to obtain a comparison image data of the same form as that obtained when the reference images data was obtained.
For example, if the distance between the scope portion of the endoscope apparatus and the observation area differs when the reference image data and the comparison image data are obtained, the magnification rate of the reference image data and the comparative image data differ, and when these images are displayed on a monitor or the like, even if the size of the diseased portion is the same, different sized diseased portions are displayed. Further, if the rotational angle of the distal end of the scope portion of the endoscope apparatus is different when the reference image data and the comparison image data are obtained, the imaging (rotation) angle of the reference image data and the comparison image data differ, and when these images are displayed on a monitor or the like, even the same diseased is displayed having different display angles.
That is to say, because there are many cases in which the magnification or display angle of the displayed diseased portion of a reference image and comparison image used to perform a comparative diagnosis is different, it is difficult for the diagnostician to immediately provide the diagnosis. In particular, because it is difficult to compare the finer differences in the images, a problem arises in that when a detailed comparison is to be performed, the efficiency of the diagnosis is lowered. Further, though it is possible to manually adjust the magnification or display angle of the diseased portion, aside from requiring a cumbersome manual operation, it is very difficult to accurately match the display angle or magnification of the diseased portion by sight, leading to difficulty in performing a detailed comparison and lower diagnostic efficiency.
Further, if, for example, the imaging angle of the distal end of the scope portion of the endoscope apparatus with respect to the observation portion differs, the form of the portion obtained as the reference image data and the form of the portion obtained as a comparison image data differ. Therefore, when these image data are displayed on a monitor or the like, even if the form of the diseased portion is the same, diseased portions having different forms are displayed. Further, when the reference image and the comparison image are obtained, there are cases in which the form of the diseased portion changes due to elongation or the like of the tissue structure itself, whereby diseased portions having different forms are displayed in this case also, leading again to low diagnostic efficiency.